Time-based State Control Method for Quantum Systems

Abstract

An exemplary quantum-based integrated circuit (IC) and method of time-based control are disclosed for a quantum computing system that controls the phase of the RF signal by delaying a clock signal and interpolating between the clocks as cryo-CMOS control of a fluxonium qubit. The exemplary architecture can generate control signals with tunable phase and integrated envelope values at a frequency f q close or equal to the quantum transition frequency to manipulate a quantum state, e.g., for a fluxonium device or a transmons device.

What is claimed is: 
     
         1 . A system comprising:
 a quantum processor; and   control electronics coupled to the quantum processor to resonantly or close to resonantly drive the quantum processor via a radiofrequency output (e.g., radiofrequency pulsed output) to manipulate a quantum state, the control electronics comprising:
 a signal generator; and 
 time-based control circuits coupled to the signal generator to generate the radiofrequency output with tunable phase and integrated envelope values at a frequency close or equal to the quantum transition frequency to manipulate a quantum state. 
   
     
     
         2 . The system of  claim 1 , wherein the time-based control circuits comprises:
 a set of cascading time delay circuits configured to receive a clock signal from the signal generator to generate a set of consecutive time-delayed clock signals; and   a multiplexor and phase interpolator configured to selectively delay the set of consecutive time-delayed clock signals to control and tune the phase and integrated envelope of the radiofrequency output.   
     
     
         3 . The system of  claim 2 , wherein the control electronics are configured to provide less than 1 mW/qubit. 
     
     
         4 . The system of  claim 1 , wherein the quantum processor comprises a set of fluxonium devices or a set of transmon devices with more than 100 qubits. 
     
     
         5 . The system of  claim 2 , wherein the set of cascading time delay circuits is implemented in an integrated circuit, the set of cascading time delay circuits comprising a delayed-locked loop circuit, a voltage-controlled delay circuit, an equal-delay buffer inverter circuit, a phase-frequency detector circuit, or a charge pump circuit. 
     
     
         6 . The system of  claim 1 , wherein the control electronics further includes a sequence controller and memory circuit coupled to the set of cascading time delay circuits, the sequence controller configured to retrieve a set of pulse and sequence outputs from the memory circuit and provided the retrieved set of pulse and sequence outputs as phase and amplitude control bits to the multiplexor, the phase interpolator, and the output circuitry. 
     
     
         7 . The system of  claim 1 , wherein the control electronics are configured as a 1-qubit controller. 
     
     
         8 . The system of  claim 1 , further comprising N−1 control electronics for an N-qubit controller having N number of qubits configured to operate at different frequencies, wherein the control electronics are configured as a master mode and the N−1 control electronics configured as a slave mode. 
     
     
         9 . The system of  claim 1 , further comprising K×N control electronics for a K×N-qubit controller having K number of Qubit configured to operate at a shared frequency, and each of the K qubits has an N number of Qubit configured to operate at different frequencies, wherein the control electronics is configured as a master mode and the K×N−1 control electronics configured as a slave mode, and wherein at least one circuitry is shared for same-frequency qubits. 
     
     
         10 . The system of  claim 1 , wherein the quantum processor comprises a set of transmon devices. 
     
     
         11 . A method comprising:
 resonantly or close to resonantly driving a quantum processor via a radiofrequency output via control electronics to manipulate a quantum state; and   adjusting the radiofrequency output via time-based controls by tuning phase and integrated envelope of the radiofrequency output at a frequency close to or equal to the quantum transition frequency to manipulate a quantum state.   
     
     
         12 . The method of  claim 11 , wherein the method comprises:
 receiving a clock signal from a signal generator;   generating a set of consecutive time-delayed clock signals; and   selectively delaying the set of consecutive time-delayed clock signals to control and tune the phase and integrated envelope of the radiofrequency output.   
     
     
         13 . The method of  claim 12 , adjustments consume less than 1 mW/qubit operation. 
     
     
         14 . The method of  claim 11 , wherein the quantum processor comprises a set of transmon or fluxonium devices with more than 100 qubits. 
     
     
         15 . The method of  claim 12 , wherein generating a set of consecutive time-delayed clock signals is performed using a delayed-locked loop circuit, a voltage-controlled delay circuit, an equal-delay buffer inverter circuit, a phase-frequency detector circuit, or a charge pump circuit. 
     
     
         16 . The method of  claim 1 , further comprising:
 retrieving a set of pulse and sequence outputs from a memory circuit; and   providing the retrieved set of pulse and sequence outputs as phase and amplitude control bits to adjust the radiofrequency output.   
     
     
         17 . The method of  claim 11 , wherein the operation controls 1 qubit. 
     
     
         18 . The method of  claim 11 , wherein the operation, as a master mode, additionally controls N−1 Qubit in slave mode. 
     
     
         19 . The method of  claim 11 , wherein the operation, as a master mode, additionally controls (K×N)−1 qubit in slave mode. 
     
     
         20 . The method of  claim 11 , wherein the quantum processor comprises a set of transmon devices.